Deleting The End of A String With BM

I'm trying to code a mock console in BlitzMax and can't figure out how to take off the last character of a string. I've tried just setting the last character to "", reducing the length of the string (with the .length variable), and copying all the contents from one string (minus the last character) to another string and the setting it back to the original. Is there just a delete function I'm unaware of?

Also, how can I limit how fast the program gets keyboard input? It's adding about 4-10 characters each time I push a button because the frames go by so quickly.